摘 要：
Crop straw is one of the main wastes in agricultural production; it contains nitrogen, phosphorus, potassium and trace elements. Crop straw resource in China is very rich, the current annual output of crop straw is about 6×10~8-8×10~8 t. However, only 1/4 of the straw are returned to field, some are used for animal feed, or for fuel, but a large number of straw are burned, or piled up or abandoned. This not only wastes valuable resources, but also causes environmental pollution. For example, the burning of straw will cause soil water evaporation, soil structure destruction, the soil compaction, the soil fertility decline, and deteriorate of soil ecological system accompanied by a crop yield decline. In recent years, with the continuous promotion of conservation tillage, straw returning is gradually accepted by farmers, and the proportion of harvested straw used for returning to the fields has been increasing year by year. The straw returning has benefit to the soil physical and chemical properties. Straw deep bury could facilitate nutrient release through decomposition process, increase soil organic matter content, reduce soil bulk density, increase soil porosity, and improve soil structure, water retention and aeration. Farmers in the three Northeast provinces of China always use small tractor to till their land in recent year, leading to problems of shallow plough layer, soil compaction, and reduction of soil water storage capacity. In view of this phenomenon, combined with the deep straw returning technology, it is needed to develop a machine that is suitable for soil conditions of the Northeast provinces. In order to improve the structure of soil layer, soil water storage, fertilizer use efficiency and increase in organic matter, and solve the problem of straw returning mode of rain fed land in Northeast China,we designed and manufactured 1 JHL-2 type returning corn straw machine, which mainly consisted of straw crushing device, conveying device, disk opener, spiral type opener, hopper device, covering device and pressing device. It can complete the straw collection, deep ditching, straw returning, covering and packing. This machine is suitable for the technical requirement of reasonable arable layer in the brown soil region of the South Central Plain of the Northeast Plain. Compared with the other traditional straw collecting machines, this one is quite different on method of collecting straw. It combined the collecting and transporting device to collect and transport the straw, Stubble cleaning device had high rotation speed and it could produce strong negative pressure, this negative pressure picked up the straw to the dam-board, then gathered on the aggregate plate, waiting for the elastic claw. The stubble device operating width is 120 cm, the conveying device operating width is 80 cm. The ditching device adopted a spiral cutter type furrower, with 40 cm furrow width and 30 cm trenching depth. This machine collected two ridge straw and bury in furrow, realized interleave deeply bury. It can not only meet the technical requirements of deep straw returning to the field, but also reduce the consumption of mechanical power. Based on the analysis of straw throwing speed by conveying device and soil particles relative to the spiral type opener device speed and force analysis, the final dimension parameters of the system were determined. Through the kinematics analysis of the key components, the detailed motion parameters were optimized: the stubble shaft speed is 1 620 r/min, Y type of flail knife line speed is 40 m/s, and the speed of conveyor belt is 1.416 m/s. Through five group field tests, under the condition of machine speed of 3 km/h, the ditching device speed of 270 r/min, ditching depth of 28 cm, straw shredding and the qualified rate was 93.5%, the average value of straw buried rate was 92%. We concluded that this machine can complete straw collection, deep buried, repressing joint operations. It not only could achieve deep buried straw, enhance soil organic, realize the coexistence of weak and solid topsoil structure, but also provide reference for optimizing design and evaluation of straw deep bury and returning machine.
